Variable magnification lens assembly having two odd-lenses

ABSTRACT

A variable magnification add-lens in which a basic lens group is movable between fixed conjugate planes. An add-lens is selectively positionable in the optical axis at each end of the basic group to vary its magnification.

United State X qak] D 1111 R 3,853,387 Demaine et al. X d0 7 1 Dec. 10, 1974 [541 VARIABLE MAGNIFICATION LENS 3.600.066 11/1071 13- v601116 350/1113 ASSEMBLY HAVING wo ODD LENSES 3.672.748 6/1972 D01 et al.

3,741,621 6/1973 McCrobie "I. 350/!83 [75] Inventors: David G. A. Demaine; John M.

Palmer, both of Leeds, England [73] Assignee: Rank Xerox Limited, London,

Primary Examiner-John K. Corbin Attorney, Agent, or Firm-Robert J. Bird England [22] Filed: June 19, 1973 [21] Appl. No.: 371,458 [57] ABSTRACT A variable magnification add-lens in which a basic 350/183 350/1 lens group is movable between fixed conjugate planes. [58] d 84 220 187 An add-lens is selectively positionable in the optical 0 are axis at each end of the basic group to vary its magnifi- [56] References Cited canon' UNITED STATES PATENTS 4 Claims 1 Drawing Figure 3,592,531 7/1971 McCrobie 350/220 50L /8 SOL/9 HAVING Two ADD-LENSES This invention relates to a lens assembly.

According to one aspect of the invention there is provided a lens assembly comprising six lens elements arranged in a substantially symetrical arrangement of two groups of three elements, the outermost pair of elements of each group of three being a cemented doublet with the outermost element of each doublet being biconvex and the innermost element of each being biconcave, the innermost element of each group of three being concavo-convex with its convex surface outermost.

the main lens 21 is used in conjunction with add-lens 23, which is moved into the optical path as the main lens is moved towards upper mirror 263. The addlenses 22 and 23 are swung into and out of the optical path as the main lens moves by means of ramp cams.

In the drawing, the lens assembly is shown in the 70 percent mode position, with both the add-lenses 22 and 23 swung out of the optical path. If now the lens is brought into its 50 percent mode position, i.e. from left to right as seen in the drawing add-lens 23 is swung into the optical path. The mount 270 of add-lens 23 carries a small wheel 271 which travels along a ramp cam surface 272 as the lens is driven towards its 50 percent position. In the drawing, the position of add-lens 23 when The invention is particularly, although not exclu- IS the e is in its 50 Percent Positton is show" y broken sively, concerned with a lens assembly suitable for pro- Outhhe wh is y Visible h the adfi-lehs jecting images of an object in a selected one of plurality 23 this pesltleht .helhg out of g hehlhd mam lens of magnification modes, the lens assembly being moved as e e the drawlhg, e m the 7 -pe P along its optical axis to obtain the different magnificatlohsImllarlyvyyhen the lehs thoved Its 100 P t tions, while at the same time maintaining constant cone mode Posttloh, add'tehs 22 swhhg into the P- jugatc separation cal path by means of wheel 274 earned on the lens According to another aspect of the present invention mount 275 add-lens the wheel 274 t h there is provided a lens assembly comprising a main along a Second ramp cam h e e The Position of lens for producing an image of an object in a first magf e h the lehs Its l Peteeht mode nification mode, and two add-lenses for supplementing Posltloh ated by brolten outline 277. the main lens respectively in each of second and third Refemhg e more particularly to the lenses, the magnification modes in which the main lens is moved math h eohslsts t elements, numbered t0 6 from along its optical axis inone direction in the second left to hght a$ $eeh the y g T e lens is of genermode and in the opposite direction in the third mode, any Symmetteet eohhgutahoh two groups of the Second and third modes producing image Sizes 30 three elements. Lens elements 1 and 2 are a cemented which are respectively greater and smaller than the doublet: as are lens elemehts 5 h Elements 1 and image Size produced in the first mode. 6 are bi-convex lenses Wlth their innermost surfaces A lens assembly in accordance With the present having a very large radius of curvature. Lens elements vcnticn will now be described by way of example only 2 and 5 are bl-concave elements, with their outer surwith reference t0 the accompanying drawing which is faces cemented to the inner surfaces of elements 1 and a cross Sectional elevation of the lens assembly 6 respectively. Lens elements 3 and 4, the innermost Referring to the drawing there is Shown a lens assem elements of each set of three elements, are concavobly for use in a copying machine, d for producing convex elements, withthelr convex surfaces outermost. copies in any one of thrce magnification modes, while The refractive mdlces of elements 2 and 5 are less than maintaining, by movement of the lenses only, a conthose of any of othetcelemehts Stam conjugate length Forming part f the Optical The constructional details of the main lens are set out sembly of the machine are a first mirror 262, and a sech table 1 below ond mirror 263, which are mounted kinematically, so ht the 50 Percent mode, the add-let's 23 is brought that there is no residual force moment about the plane into the pti a P 80 that there is nly a Short air ofthe mirrors. The mirrors, and other parts ofthe optisp ce b ee jace ur o the two ense cal ystem of the machine (not hown in the drawing) Add-lens 23 consists 0f [W0 lens elements 7 and 8, eleremain in fixed positions, regardless of the magnificant 7 being a bi-concave element. a element 8 i d l t d, being a bi-convex element. Table 2 below sets out the Th three ifi ti modes are a 100 percent constructional parameters of the percent add-lens mode, in which the copy is substantially the same size 50 23. as the original document; and two reduction modes, in In the 100 percent mode, add-lens 22 is brought into which the copy is respectively percent and 50 perthe optical path, with only a short air space between the cent of the size of the original document. In the 70 peradjacent lens surfaces. Add-lens 22 consists of two lens cent mode, only the main lens 21 is used, whereas in 55 elements 9 and 10, element 9'being a bi-concave elethe percent mode, add-lens 22 is swung into the ment, and element 10 being a bi-eonvex element. Table optical path as the main lens 21 is moved to a position 3 below gives the constructional parameters for the 100 closer to the first mirror 262. In the 50 percent mode, percent add-lens 22.

TABLE 1 ITEM RADIUS AXIAL THICKNESS REFRAC- CLEAR (inches) (inches) IJllJ E X APER- TURE OBJECT PLANE 047240 A PLATEN PLANE AIR 28.4!036 1.0 LENS 1 3.4665 4.02

TABLE 1-C0ntinued ITEM RADIUS AXIAL THICKNESS REFRAC- CLEAR t' TIVE (inhes) (inches) INDEX APER- TURE LENS 2 216.772 3.38

AIR 0.18611 1.0

LENS 3 4.2202 2.56

AIR 0.68583 1.0

STOP 1.43

AIR 0.70228 1.0

LENS 4 6.5586 2.34

AIR 0.22659 1.0

LENS 5 2.5575 2.64

LENS 6 216.772 3.57

AIR 19.6750 1.0

IMAGE SURFACE TABLE 2 ITEM RADIUS AXIAL THICKNESS REFRAC- CLEAR TIVE (inches) (inches) INDEX APER- TURE OBJECT AS TABLE 1 PLATEN AIR 31.90741 1.0

LENS 1 LENS 2 AIR AS TABLE 1 LENS 3 AIR STOP 1.14

AIR LENS 4 AIR AS TABLE 1 LENS 5 LENS 6 AIR 0.20 1.0

LENS 7 -I4.0010 4.35

AIR 0.06 1.0 LENS 8 25.078 4.85

AIR 15.19145 1.0

IMAGE SURFACE TABLE 3 ITEM DIUS AxIAL THICKNESS REFRAC- CLEAR T1vE (inches) (inches) 7 INDEX APER- TuRE oBIEcT AS TABLE I 'PLATEN AIR 22.64466 1.0

LENS 9 57.038 4.91

AIR 0.11770 1.0

LENS 10 7.614 4.52

AIR 0.50000 1.0

LENS 1 LENS 2 AIR AS TABLE 1 LENS 3 AIR STOP 1.73

AIR LENS 4 AIR As TABLE 1 LENS 5 LENS 6 AIR 24.43274 1.0

IMAGE SURFACE In tables 1,2, and 3, the refractive indices are as fol- AXIAL lows. ITEM RADIUS THICKNESS REFRACTIVE INDEX (inches) (inches) LENSI 3.4665 N(404.7)= 1.64185 1.20078 N(435.8) 1.63698 "(404.71 "(435.81 "(486.11 M486"):

- LENS 2 2l6.772 N 404.7 9 A 1.53735 l.53338 1.52860 027m z i 22 B 1.64185 1.63698 1.63113 70 N(486'1)= 155679 C 1.56931 1.56355 1.55679 40 D 1.64120 1.63634 1.63050 E 1.52976 1.52621 1.52190 MR F [.569l4 [.56337 L5566l LENS 3 22 N 404 7 418 G 164183 L631 3 0.30986 N24353: iI2369 6.5586 N(486.l) 1.63113 5 AIR 0.68583 7 1.0

What is claimed is: STOP VI. A lens assembly comprising six elements disposed AIR 070228 1,0 along an optIcal ax1s and arranged In a substantially LENS 4 6'5586 M404: M20 symmetrIcal arrangement of two groups of three ele- 031430 M4353) M3634 ments, the outermost pair of elements of each group of M4861 1153050 three being a cemented doublet with the outermost ele- MR 022659 w ment of each doublet being bi-convex and the innermost element of each doublet being bi-concave, the in- LENS 5 "25575 038078 $132}; 1:22;; nermost element of each group of three being concavo- 216.772 N(486.l 1 1.55679 convex w1th Its convex surface outermost, the lens as- LENS 6 2M7" M40) 4'85 sembly beIng accordmg to the followmg constructural M4532 M4353). 3698 data: 3.41I34 N(486.l 1 1.63113 AIR 19.6750 1.0

AXIAL IMAGE lTEM RADIus THICKNESS REFRACTIVE INDEX SURFACE (inches) (inches) OBJECT PLANE 047240 M4041) 53735 2. A lens assembly as defined in claim 1 further in- Pl-ATEN M4353) 153338 cludin an add-lens at each end of said assembl for se- PLANE N1486.1I= 1.52860 y lect1ve poS1tIon1ng Into saId optIcal axis to vary the AIR 28.41036 10 magnification of said lens assembly, said add-lenses lowing constructural data:

T AXIAL ITEM RADIUS THICKNESS REFRACTIVE INDEX (inches) (inches) LENS 9 57.038 N(404.7) 1.52976 0030000 N(435.8)=1.52621 7.368 N(486.1) 1.52190 AIR 0.11770 I 1.0

LENS 7.614 N(404.7) 1.52976 AIR 0.50000 1.0

LENS 1 LENS 2 AIR LENS 3 AIR STOP AIR LENS 4 AIR LENS 5 LENS 6 AIR 0.20 1.0 LENS 7 14.0010 N(404.7) 1.56914 0.30 N(435.8) 1.56337 25.7810 N(486.l)= 1.55661 AIR 0.06 1.0

LENS 8 25.078 N(404.7)=1.64183 0.44 N(435.8) 1.63696 -l3.5857 N(486.1)= 1.63111 3. A lens assembly as defined in claim 1, further including an add-lens at the end of said assembly adjacent lens 1 for positioning into said optical axis to vary the magnification of said lens assembly. said add-lens combining with said lens assembly according to the following constructional data:

AXIAL ITEM RADIUS THICKNESS REFRACTIVE INDEX (inches) (inches) LENS 9 57.038 N(404.7) 1.52976 0.30000 N(435.8) 1.52621 7.368 N(486.l 1.52190 LENS 10 7.614 N(404.7) 1.52976 0.50000 N(435.8) 1.52621 72.080 N(486.1) 1.52190 AIR 0.50000 1.0

4. A lens assembly as defined in claim 1, further including an add-lens at the end of said assembly adjacent lens 6 for positioning into said optical axis to vary the magnification of said lens assembly, said add-lens combining with said lens assembly according to the following constructional data: 

1. A lens assembly comprising six elements disposed along an optical axis and arranged in a substantially symmetrical arrangement of two groups of three elements, the outermost pair of elements of each group of three being a cemented doublet with the outermost element of each doublet being bi-convex and the innermost element of each doublet being bi-concave, the innermost element of each group of three being concavo-convex with its convex surface outermost, the lens assembly being according to the following constructural data:
 2. A lens assembly as defined in claim 1 further including an add-lens at each end of said assembly for selective positioning into said optical axis to vary the magnification of said lens assembly, said add-lenses combining with said lens assembly according to the following constructural data:
 3. A lens assembly as defined in claim 1, further including an add-lens at the end of said assembly adjacent lens 1 for positioning into said optical axis to vary the magnification of said lens assembly, said add-lens combining with said lens assembly according to the following constructional data:
 4. A lens assembly as defined in claim 1, further including an add-lens at the end of said assembly adjacent lens 6 for positioning into said optical axis to vary the magnification of said lens assembly, said add-lens combining with said lens assembly according to the following constructional data: 